The present invention relates to a multifunction speaker used in a mobile transmission instrument such as a portable telephone, PDA (Personal Digital Assistant) and video game device. The multifunction speaker is provided with a vibrating function device for informing a user when a calling signal is applied.
A conventional mobile transmission instrument such as a portable telephone and PDA is generally adapted to change the calling operation thereof from generating buzzer sounds and melodies to vibrating a case of the instrument without producing sounds for informing the user of a calling signal. In order to achieve that kind of operation, a small speaker for generating sounds and a vibrating device in which an eccentric weight is vibrated by the rotation of a small motor are provided separately in a mobile transmission instrument. However, incorporating both the speaker and the vibrating device in the instrument is disadvantageous in rendering the instrument compact and inexpensive. Thus, there has been provided a multifunction speaker capable of generating both the sounds and the vibration within a single device such as that described in FIG. 1 and paragraphs 0016 to 0019 of Japanese Patent Application Laid-Open 2001-225010.
FIG. 8 is a plan view of that kind of conventional multifunction speaker 101 mentioned above, FIG. 9 is a sectional view taken along a line IX-IX of FIG. 8, and FIG. 10 is a bottom view of the multifunction speaker 101.
Referring to FIGS. 8 and 9, the multifunction speaker 101 comprises a substantially cylindrical molded frame 102 having cylindrical portion 102a. A part of the periphery of the cylindrical portion 102a is extended to form a terminal supporting portion 102b. The cylindrical molded frame 102 has an upper stepped portion 102c. An upper first supporting spring plate 103 is mounted on a stepped portion 102c of the cylindrical portion 102a and a lower second spring plate 104 is attached on an underside 102d of the frame 102. Each of the spring plates 103 and 104 comprises an annular inner portion, annular outer portion, and a plurality of arcuate arms connecting the inner and outer portions.
On the lower second spring plate 104, there is mounted a pole piece 105 made of a magnetic material and having a center pole 105a and a flange 105b. An annular magnet 106 is securely mounted on the flange 105b and an annular top plate 107 made of a magnetic material is securely mounted on the annular magnet 106 thereby forming a magnetic circuit 112. The inner periphery of the spring plate 103 abuts on the outer edge of the top plate 107 thereby to support the top plate 107. Accordingly, the magnetic circuit 112 is resiliently supported in the frame 102 by the first and second spring plates 103 and 104.
A plastic diaphragm 108 is mounted on the upper stepped portion 102c of the frame 102 and held by a ring 110 having an L shape in section. A cylindrical coil 111 which is secured to a lower part of the diaphragm 108 is inserted in a magnetic gap G formed between the inner periphery of the top plate 107 and the outer periphery of the center pole 105a. 
A positive terminal 113 and a negative terminal 114 each having a U-shaped section are inserted in respective slits formed in the terminal supporting portion 102b of the frame 102. Each of the positive and negative terminals 113 and 114 is bent after being inserted in the slit. Both ends of the positive and negative terminals 113 and 114 have an overlapped portion, respectively. Hence a pair of external terminals are formed. Ends 111a of the cylindrical coil 111 are connected to the terminals by solders. A resin 116 is applied to protect the solders 115.
The multifunction speaker 101 further has a disk shaped metallic first protector 117, the periphery of which is embedded in the ring 110. The first protector 117 has a plurality of sound emanating holes 117a. A disk shaped metallic second protector 118 is mounted on the lower portion of the frame 102 interposing the second spring plate 104 and an annular spacer 120. The second protector 118 has a plurality of vents 118a as shown in FIG. 10.
In operation, when a driving signal of audio frequency is applied to the cylindrical coil 111, the cylindrical coil 111 generates an exciting force which interferes with the magnetism of the magnet 106. Accordingly, the diaphragm 108 is vibrated due to the attraction in the magnetic circuit 112 to generate sounds. When the frequency of the applied signal is low, while no sound is generated from the diaphragm 108, since the magnetic circuit 112 is resiliently supported in the frame 102, the relative position of the coil 111 to the magnetic circuit 112 changes, so that the magnetic circuit 112 is vibrated. The vibration is transmitted to the frame 102 causing a case in which the multifunction speaker 101 is housed to resonate. As a result, when the multifunction speaker 101 is adopted in a small instrument such as a video game device and telephone, the user is able to feel the vibration at the fingertip or other parts of the body with which the case is in contact. Hence the production of both the sound and vibration becomes possible with only one speaker.
However, in the conventional multifunction speaker, since the side periphery of the frame is not covered by a protector, external electromagnetic waves and electric field have an influence on the operation of the magnetic circuit, causing electromagnetic noises which affect the performance of the speaker. Furthermore, in the case of a conventional multifunction speaker being used in a portable telephone for example, the caused electromagnetic noises also affect the external instrument, the portable telephone here.